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Licensed Unlicensed Requires Authentication Published by De Gruyter (O) September 25, 2009

Structure and ferroelasticity of tetramethylammonium-hexafluoroosmate(IV), (TMA)2[OsF6]

H. Küppers, O. Göbel, C. Bruhn and W. W. Schmahl

Abstract

(TMA)2[OsF6] has at room temperature a rhombohedral structure (space group R3̅) which is pseudo-cubic (K2[PtCl6]-type). a = 8.0565(6) Å, c = 20.020(3) Å (hexagonal setting). Double refraction decreases linearly with increasing temperature and disappears above 434 K which indicates cubic symmetry of the high temperature phase. The change from the cubic high temperature structure to the rhombohedral structure is characterized by a ferrorotative tilt of the [OsF6] octahedra and the TMA tetrahedra. Evidence of ferroelasticity follows from the switching of the trigonal c-axis by the application of directional pressure. The phase transitions of (TMA)2[OsF6] (Fm3̅ m → R3̅) and of the recently reported (TMA)2[PtF6] and (TMA)2[IrF6] (FmmI4/m) are described by Landau’s theory.

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Published Online: 2009-9-25
Published in Print: 2001-6-1

© 2001 Oldenbourg Wissenschaftsverlag GmbH

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